Body wall and body cavity

The outer body wall (epidermis) contains hairlike projections (cilia) in most echinoderms except ophiuroids; the body wall of crinoids has relatively few. The cilia produce a waving motion that carries food particles toward the mouth or removes unwanted particles from the body. The epidermis also contains glandular and sensory cells. The epidermis of skeletal elements such as spines and pedicellariae, which project from the body surface, often is worn away. The next layer, the dermis, includes the calcareous skeleton and connective tissues. Internal to the dermis are circular and longitudinal muscle layers. The ... (100 of 9,068 words)